This invention provides an improved method for disposing of bubbles in dispersions of polyvinyl fluoride (PVF) in latent solvents, followed by coating at appropriate high viscosities.
Polyvinyl fluoride (PVF) is generally not soluble at room temperature in conventional solvents, however, it can be put into solution with so-called latent solvents. A dispersion of PVF powder is suspended in latent solvent and heated to a first temperature at which a gel is formed and then to a higher second temperature at which a solution is formed. Latent solvents and other technology useful in handling PVF are discussed in U.S. Pat. Nos. 2,953,818--Bartron (Sept. 27, 1980) and 3,139,470--Prengle et al. (June 30, 1964), both incorporated herein by reference.
Various additives to latent solvent dispersions have been proposed, including N-acetyl substituted piperidine and morpholine in U.S. Pat. No. 3,110,692--Proctor (1963). U.S. Pat. No. 3,779,976--DeMarsico et al. (1973) proposes the use of an isopropanol solution of polymers containing acid groups and polymers containing oxazolidine groups.
Optimum techniques have not been proposed for disposing of bubbles in a dispersion with low viscosity, followed by painting with the dispersion at a high and constant enough viscosity.